It’s hard to believe that we’re already heading towards the tail-end of summer! Even though we’re still harvesting baskets full of summer produce from our garden, we’ve just started many of our fall seeds indoors to get a jump start on the cool weather gardening season.

Bok choys and other cool weather plants sprouting. These will be transplanted outdoors in late summer for the fall garden.

Bok choys and other cool weather plants sprouting. These will be transplanted outdoors in late summer for the fall garden.

This is also the time of year that your summer plants might start showing signs of bacterial or fungal disease. For instance, your tomatoes might have septoria leaf spot; your squash might have powdery mildew, etc..

The good news is that there are steps you can take to easily prevent and/or stop plant diseases in your summer garden. Doing so will help you increase your summer yields. Some of these recommendations will also help you improve the biological fertility of your soil, which means healthier plants and larger yields from your upcoming fall and winter garden as well!

1: Focus On Soil Health (Prevention)

Biological systems and lifeforms are complex beyond comprehension. As such, it’s much easier to practice prevention than treatment. The same applies to people. For instance, it’s much easier NOT to ingest sodas and highly processed foods than it is to try to treat Type II Diabetes.

Likewise, it’s important for you to understand that the foundation of any organic garden or farm is the health of its soil. Without healthy soil, trying to grow plants will be a never-ending battle of treating symptoms.

This is a soil profile from Tyrant Farms showing a young Jerusalem Artichoke growing in a no-till organic garden bed. The soil started off as brick hard, red clay. After top-dressing the bed with leaf and wood chip mulch (rather than tilling), you can see clearly how soil organic matter and soil structure has been drastically improved in a short period of time by trillions of macro and microorganisms.

This is a soil profile from Tyrant Farms showing a young Jerusalem Artichoke growing in a no-till organic garden bed. The soil started off as brick hard, red clay. After top-dressing the bed with leaf and wood chip mulch (rather than tilling), you can see clearly how soil organic matter and soil structure has been drastically improved in a short period of time by trillions of macro and microorganisms.

When we say “healthy soil” we simply mean soil that has all the biological life forms present to:

a) feed your plants all the macro and micronutrients they need while optimally cycling nutrients and water, and

b) protect your plants from pathogenic/disease-causing organisms.

If you’d like to learn more about how to build the biological fertility of your soil, read our March 2016 Tip of the Month article.

2: Stop Powdery Mildew on Squash, Pumpkins, Cukes, and Other Cucurbits

A healthy zucchini plant. “Powdery mildew” is a fungal disease that looks like white splotches of powder on the leaves of your cucurbit leaves, especially during hot humid/wet weather.

A healthy zucchini plant. “Powdery mildew” is a fungal disease that looks like white splotches of powder on the leaves of your cucurbit leaves, especially during hot humid/wet weather.

Powdery mildew” is the common name given to any number of fast-growing, airborne fungal diseases that cause white powdery patches on the leaves of cucurbits and other garden plants. Left untreated, powdery mildew causes the leaves to turn brown and dry out, eventually killing the plant.

(picture of summer squash)

Break out the fungicides? No! Not unless you want to also kill the beneficial fungi in your garden that help your plants.

Powdery mildew can be easily prevented using organic methods. The easiest, most proven method of treatment involves milk. (Yes, that white liquid from cow utters.) Make a mixture of milk and water (30% milk to 70% water is fine) and spray it evenly on the surface of the leaves of affected plants during the morning on a sunny day.

Any type of milk will work: skim or whole. In studies, this method has proven to be as effective as any synthetic fungicide in stopping powdery mildew, although scientists aren’t quite sure how it works (likely an antiseptic effect resulting from the sun burning the fungus as it’s bound by the milk protein).

3: Prevent or Stop Tomato Foliar Diseases

If you live in the hot humid south like we do, it’s extremely unlikely that you’ll get through a whole summer without seeing some type of foliar (leaf) disease on your tomato plants, especially if you’ve been growing tomatoes for more than a year without “crop rotation” (e.g. not planting the same type of plant in the same spot year after year). There are probably hundreds if not thousands of bacterial, fungal, or viral tomato foliar diseases, so we’re not going to bother to get too specific here.

We recommend fighting biology with biology. This is the start of a hot compost pile using the Berkeley Composting Method (developed by Berkeley University). The pile is turned every 48 hours to prevent it from going aerobic or getting too hot. The internal temperatures hit 140+ degrees F for over 10 days, pathogenic microorganisms and seeds are

We recommend fighting biology with biology. This is the start of a hot compost pile using the Berkeley Composting Method (developed by Berkeley University). The pile is turned every 48 hours to prevent it from going aerobic or getting too hot. The internal temperatures hit 140+ degrees F for over 10 days, pathogenic microorganisms and seeds are “burned” out, leaving only good biology for you to work with. Using this method, you can go from start to finished compost in as little as 3 weeks. The compost can be applied to your soil surface or made into an aerated “tea” to be used as a soil drench of foliar spray.

What’s the best organic way to prevent or stop tomato foliar diseases? For prevention and treatment, we recommend either:

  1. Actively Aerated Compost Tea (AACT) – We recommend making AACT from hot compost (Berkeley Method) or non-anaerobic worm castings (worm castings that have been stored in an airtight container, a hot place, or in a liquid will have mostly dead microbes that aren’t a good inoculate for compost tea).
    • How To Use It – Apply AACT as a foliar spray throughout the growing season; also apply as a soil drench 1-2 times per year during seasonal transitions (summer > fall garden or winter > spring garden). During particularly rainy periods when disease pressure will be higher, you might want to increase application frequency.
    • How It Works – The best analogy here is the human microbiome, e.g. the trillions of microorganisms in and on you that play a wide range of roles in keeping you healthy and alive. If your gut flora is out of balance, it can have profound impacts on your physical and even psychological health. The same is true with plants. By keeping their leaf surfaces coated with beneficial bacteria, fungi, etc, you make it exponentially more difficult for pathogenic microorganisms to take hold or proliferate. Similarly, you can keep soil-borne pathogens in check by applying AACT as a soil drench.
  2. Serenade – If you want to take the easier, store-bought approach, we recommend using Serenade (you can buy it here). Serenade is OMRI listed for organic farms and gardens.
    • How To Use It – Use preventatively as a foliar spray or immediately upon seeing signs of disease on your tomato plants’ leaves. You can buy it as a pre-diluted, ready-to-use spray bottle or in concentrate to mix at home as-needed.
    • How It Works – Serenade is a patented strain of bacteria (Bacillus subtilis) that basically eats many types of pathogenic bacteria and fungi or outcompetes them for prime real estate on the surface of your plants. Actinovate is another excellent bio-based organic product that is also excellent at preventing or stopping plant diseases.

4: Proper Irrigation Methods

We recommend using drip irrigation rather than overhead irrigation or sprinklers.

Drip irrigation line. Photo cc license courtesy of JobyOne.

Drip irrigation line. Photo cc license courtesy of JobyOne.

Irrigating your plants with a sprinkler/overhead irrigation is less water efficient than irrigating through drip lines (overhead sprinklers can lead to water losses up to 50% due to evaporation). Also, sprinklers cause your plants’ leaves to get wet and therefore makes them more prone to infection by pathogenic fungi and bacteria (foliar diseases). If you absolutely have to use sprinklers, irrigate in the early morning to maximize water efficiency and give your plants’ leaves plenty of time to dry off!

5: Don’t Touch and Spread!

Want to touch and cuddle your plants? We’re gardeners too so we know how you feel! But if your plants’ leaves are either: a) wet, or b) showing signs of disease (discoloration or spotting) outside of normal seasonal color changes as the weather cools, you need to learn to control your plant-touching urges. Otherwise, you might well end up spreading a foliar disease to other plants in your garden.

Concord grapes at Tyrant Farms. Always clean your clippers between trimming different plants!

Concord grapes at Tyrant Farms. Always clean your clippers between trimming different plants!

On a similar note, be sure to practice good “clipper hygiene” by washing or disinfecting your garden tools between uses–especially if you’ve used those tools to remove diseased plants or plant foliage. Rubbing alcohol or scalding hot soapy water should do the trick.

(picture of glass with rubbing alcohol in it, covered with seran wrap and clippers next to it)

You wouldn’t want to see a doctor performing surgery on a patient without first disinfecting their hands and surgical tools, would you? The same principle applies to your garden plants. Be a good plant doctor!

Just in case you’re not already a GrowJourney Seeds of the Month Club member, we’d love for you to give us a try (for free) to see if you’d like to start growing with us! And don’t forget: a GrowJourney Gift Membership also makes a unique and special gift.




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